Assy 250425 Rev. B #1

The machine would boot normally, but Control Port 2 showed faults using my 64 Doctor Cartridge. Nothing happened when pushing fire, right or left with a joystick.

The control ports are closely connected to the CIA chip at U1 (MOS 6526). I therefore started checking the physical connections (traces) from the control port to the chip as I’d previously ‘cured’ a faulty Control Port by exchaning this chip (link). All connections checked out OK.

I therefore replaced the CIA chip with a working one.

And now both Control Ports are working again and the machine is ready to do some gaming!